1. Field
A scroll compressor is disclosed herein.
2. Background
In general, scroll compressors are widely used for refrigerant compression in air-conditioning apparatuses, for example, as they have advantages of obtaining a relatively higher compression ratio compared to other types of compressors, and acquiring a stable torque resulting from smooth strokes for suction, compression, and discharge of the refrigerant. The behavior of the scroll compressor is dependent on shapes of a fixed wrap and an orbiting wrap. The fixed wrap and the orbiting wrap may have a random shape, but typically, they have a shape of an involute curve, which is easy to manufacture. The term “involute” curve refers to a curve corresponding to a track drawn by an end of a thread when unwinding the thread wound around a basic circle with a predetermined radius. When such an involute curve is used, the wrap has a uniform thickness, and a rate of volume change of a compression chamber is constantly maintained. Hence, a number of turns of the wrap is increased to obtain a sufficient compression ratio, which may, however, cause a size of the compressor to be increased corresponding to the increased number of turns of the wrap.
The orbiting scroll typically includes a disk, and the orbiting wrap is located on one side of the disk. A boss is formed at a rear surface of the disk opposite to the side on which the orbiting wrap is formed. The boss is eccentrically connected to a rotational shaft, which is coupled to a rotor of the motor, so as to allow the orbiting scroll to perform an orbiting motion. Such an arrangement allows the orbiting wrap to be formed on almost an entire surface of the disk, thereby reducing a diameter of the disk for obtaining a uniform compression ratio. However, as the orbiting wrap and the boss are spaced from each other in an axial direction, a point of application of a repulsive force of a refrigerant applied upon compression and a point of application of a reaction force, which is opposed to the repulsive force of the refrigerant, are spaced apart from each other in the axial direction. Accordingly, the repulsive force and the reaction force are applied to each other as a torque during operation of the compressor. This causes the orbiting scroll to be inclined, thereby generating more vibration and noise.
To solve this problem, for example, Korean Patent Registration No. 10-1059880 has introduced a scroll compressor in which a coupled portion between a rotational shaft and an orbiting scroll is located on a same plane as an orbiting wrap. This type of scroll compressor can solve the problem that the orbiting scroll is inclined because a point of application of a repulsive force of a refrigerant and a point of application of a reaction force against the repulsive force are opposed to each other at a same height.
Scroll compressors in which an eccentric portion of a rotational shaft and an orbiting wrap of an orbiting scroll are coupled to each other in an overlapping manner are classified into a top compression type scroll compressor, in which a compression unit or device is located above a motor unit or motor, and a bottom compression type scroll compressor, in which the compression unit is located beneath the motor unit.
In structures of the top compression type scroll compressor and the bottom compression type scroll compressor, the rotational shaft is inserted up to a height where it overlaps the orbiting wrap of the orbiting scroll, which results in a reduction in a space for forming the orbiting wrap based on a same disk. Accordingly, to increase a compression ratio with respect to the same disk, a bearing area of a coupled portion between the rotational shaft and the orbiting wrap should be reduced as little as possible, ensuring a high bearing performance of the coupled portion.
In order to increase the bearing performance of the coupled portion between the rotational shaft and the orbiting scroll, a smooth oil supply should be ensured, and this is very important with respect to the reliability of the compressor. For the top compression type scroll compressor, the oil supply may be difficult due to a large distance between an oil storage space and the compression unit, and a great deviation of an amount of oil supplied is caused according to an operating speed of the compressor. On the other hand, for the bottom compression type scroll compressor, a relatively uniform oil supply is enabled in view of a short distance between the oil storage space and the compression unit; however, the oil supply may be structurally difficult.
For example, in a scroll compressor in which an eccentric portion of the rotational shaft and the orbiting wrap of the orbiting scroll overlap each other in a radial direction, a portion compressed by the orbiting scroll and a portion to which oil is fed are not separated from each other, and the eccentric portion of the rotational shaft is coupled to a rotational shaft coupling portion through the disk of the orbiting scroll. This may cause a high pressure refrigerant, leaked from a compression chamber, to be introduced between the eccentric portion and the rotational shaft coupling portion. If an oil-feeding hole connected to an oil passage is formed through an outer circumferential surface of the eccentric portion, the high pressure refrigerant leaked from the compression chamber may block (shield, close) the oil-feeding hole. Accordingly, the oil flowing in the oil passage may fail to flow between the eccentric portion and the rotational shaft coupling portion, thereby delaying the oil supply.
Also, in such a scroll compressor, a repulsive force generated due to a gas force is applied at about a 90° point along a rotational direction of the rotational shaft, based on a line connecting a center of the shaft (or an axial center) and a center of the eccentric portion. Hence, a section with a highest oil pressure distribution, namely, an oil feeding-required section in which the oil supply is needed may be formed in a range of about a 90° point up to a 180° point, along the rotational direction of the rotational shaft from an eccentric direction of the eccentric portion. However, if an outlet of the oil-feeding hole or an oil-feeding slit is located far away from the oil feeding-required section, oil may not quickly move to the oil feeding-required section, thereby causing a bearing performance to be reduced. Meanwhile, if the oil-feeding hole or the oil-feeding slit is formed within the oil feeding-required section, oil may not be sufficiently drawn out due to high internal pressure of the oil feeding-required section, thereby reducing oil supply efficiency.